1. Field of the Invention
This present invention is related to a photo sensor, a method of forming the photo sensor, and a related optical touch device, and more particularly, to a photo sensor having a silicon-rich (Si-rich) dielectric layer, a method of forming the same, and a related optical touch device.
2. Description of the Prior Art
Photo sensors are widely applied in various types of thin film transistor (TFT) display. The current photo sensors mostly use III A group elements and V A group elements to form positive-intrinsic-negative (PIN) diodes. The PIN diode sensors, however, have low optical absorption efficiency and are easily to be influenced by non-target light source (noise), and therefore have low signal to noise ratio. In addition, for the TFT displays, the process adjustment of the PIN diode sensors is limited by the TFT characteristics and the materials of the PIN diode made of III A group element and VA group element. Therefore, the conventional PIN diodes have the limitation in the application and manufacturing capacity.
On the other hand, the industry also develops, utilizing the high photosensitivity of the amorphous silicon (α-Si), to fabricate the thin film transistor sensor (TFT sensor) using the amorphous silicon. Please refer to FIG. 1, which is a schematic diagram illustrating a conventional amorphous silicon photo sensor. The conventional amorphous silicon photo sensor 10 includes a first electrode 12, a second electrode 14, and an amorphous silicon layer 16 disposed between the first electrode 12 and the second electrode 14. When visible light beams irradiate on the amorphous silicon layer 16, the amorphous silicon layer 16 can be excited to generate photo current. However, the amorphous silicon TFT sensor also has the disadvantage of low photo current stability. Even without operating the sensor, photo current is easily decreased as time goes by so that the severe reliability issue exists. Besides, the major sensing range of the amorphous silicon TFT sensor is in the visible light range, and the infrared (IR) rays sensing ability of the amorphous silicon TFT sensor is lower. Therefore, the sensing ability of the amorphous silicon TFT sensor is limited.
As a result, the current photo sensors in the industry can no longer fulfill the requirement in many optoelectronic application and new generation photo sensors become the major issue in the research and development.